Update, 12/23/2019: CheckBook and CheckBook Pro 2.6.11 work around the issues with FAT volumes so your documents on external or removable volumes formatted as FAT16 or FAT32 should now work just fine.
Update, 11/20/2019: CheckBook and CheckBook Pro 2.6.9 are now available and resolve the issue of storing your document on an external or removable volume, but we’ve discovered the fix won’t work with FAT16 or FAT32 volumes. These are DOS/Windows formats that most USB thumb drives and hard drives are pre-formatted with, and many Mac users aren’t aware their drives are formatted this way until subtle issues like this crop up over time. If your external or removable volume is formatted with FAT16 or FAT32, continue using the copy of your document on your Mac’s startup volume and we’ll keep plugging on a fix for the next minor update to CheckBook and CheckBook Pro.
Update, 11/18/2019: CheckBook and CheckBook Pro 2.6.9, with fixes for this issue and more, made their way to the mothership over the weekend. We expect the updates to be approved on Tuesday so keep an eye out!
We’re investigating an issue affecting CheckBook and CheckBook Pro folks who’ve upgraded to macOS Catalina, where their document is stored on an external drive, resulting in the application telling the user the document can’t be accessed because of a permissions issue. This isn’t something CheckBook itself causes, as far as we can tell, but we’re on the case, learning more details, and will update you here with what we find. In the meantime, if you have your document on an external or removable drive and get an error about permissions, your data is safe but needs to be copied to your startup drive. Copy your document to your Documents folder and double-click it there. CheckBook will open that copy automatically going forward. Stay away from the original copy on the external drive until we get to the bottom of this, and get in touch at firstname.lastname@example.org if you need any help before then!